Digital lighting technologies, i.e. illumination based on semiconductor light sources, such as light-emitting diodes (LEDs), offer a viable alternative to traditional fluorescent, HID, and incandescent lamps. Functional advantages and benefits of LEDs include high energy conversion and optical efficiency, durability, lower operating costs, and many others. Recent advances in LED technology have provided efficient and robust full-spectrum lighting sources that enable a variety of lighting effects in many applications. Some of the fixtures embodying these sources feature a lighting module, including one or more LEDs capable of producing different colors, e.g. red, green, and blue, as well as a processor for independently controlling the output of the LEDs in order to generate a variety of colors and color-changing lighting effects, for example, as discussed in detail in U.S. Pat. Nos. 6,016,038 and 6,211,626, incorporated herein by reference.
It has been proposed to utilize an LED light source in lieu of one or more incandescent light sources in various lighting fixtures such as, for example, lighting fixtures designed for theatrical and other entertainment applications. The LED light source in such lighting fixtures generally attempts to replicate the light output of the incandescent source.
However, such lighting fixtures utilizing a LED light source suffer from one or more drawbacks. For example, the LED lighting fixtures may employ LEDs of multiple colors and may be unable to obtain efficient mixing of the colors. Inefficient mixing of the colors may cause chromatic aberration or separation of the colors in the far field image, which may be further exacerbated when gobos or other effects are utilized. Miniature LED and Chip-on-Board arrays have reduced such an effect, but there is still a need for further mixing of the light output from the LEDS.
Thus, there is a need in the art to provide a LED-based lighting unit that provides satisfactory mixing of light output from a plurality of LEDs thereof, thereby providing minimization of chromatic aberration in the light output thereof.